Sensor-controlled automatic actuation of motorized tailgates of motor vehicles is known in the art.
Utility model document DE 20 2005 020 140 U1 describes a motor vehicle door arrangement with at least one motor vehicle door and a drive for motorized movement of the motor vehicle door from the closed position into the open position and from the open position into the closed position. The arrangement further comprises a control for triggering the drive, the control being assigned an optionally actuatable mobile part which the user generally carries and which interacts with the control means over a wireless transmission link when the user approaches the motor vehicle, enhanced activation automatically carrying out opening and/or a closing as triggered by a predetermined process of use and without the necessity of activating the mobile part. In one embodiment, provision is made for a user-side operator control event, namely a user-side foot movement, to cause the motorized opening of the tailgate. With respect to enhanced activation, the control means, especially with the vehicle stopped, can be moved into the activated and deactivated states, and can be triggered by the predetermined usage process exclusively when the control means is in the activated state.
Further, international application WO 2012/084111 A1 describes a closure element assembly of a motor vehicle having a motor-displaceable closure element, wherein a sensor assembly and a sensor controller are provided for generating an operating message. By means of the operating message, motor displacement of the closure element can be triggered. The sensor controller monitors the sensor-measured values during operating event monitoring. During fault situation monitoring, the sensor controller monitors the sensor-measured values for the occurrence of a behavior that is characteristic of a fault situation.
During the fault situation monitoring process, the sensor controller increments a “fault indicator” variable if an indication of a fault is registered at the monitoring time and, when a predetermined threshold value for the fault indicator is exceeded, a fault situation is registered as true in the sensor controller. The sensor controller generates an operating message only when, according to the two monitoring actions, an operating event but no fault situation is present.
An operational reliability of the above-presented prior art application crucially depends on an ability of the employed method for detecting an occurrence of an operator-intended event in surroundings comprising noise, for instance from interfering objects, whose magnitude may suffice to reach any predetermined threshold value set for triggering.
In the above-described systems of the prior art, when a foot or leg approaches a sensor, a sensor-generated signal is increasing. When a specified threshold is crossed, the system performs advanced measurements to validate/invalidate the foot movement.
Defining a low fixed specified threshold value, in order to start advanced measurements as soon as possible to react quickly to an event, is not viable if the signal noise is too high. The specified threshold would be crossed too often, and this would result in excessive power consumption.
Conversely, defining a high fixed specified threshold value in order to be protected against noise could result in a poor system performance, as the reaction to the event would occur in a delayed way.